This is a randomized, double-blinded, sham-controlled study comparing sham and continuous tDCS combined with repetitive upper extremity functional task training in a virtual environment. Subjects will be randomized to 1 of 2 groups: Armeo training with continuous tDCS, or sham tDCS through a randomization stratification approach. Subjects will be grouped into strata defined by the degree of weakness, and then randomized separately within each stratum according to a block randomization of 6 to receive Armeo training-continuous tDCS, or Armeo training-sham stimulation. Each subject will receive 10 training sessions over 2 weeks. Training sessions will last for 40 minutes and will focus on repetitive tasks using the Armeo device that incorporate multidirectional reaching, grasp and release action of the hand. We will use a variety of virtual tasks (computer games) in the training. Examples of the virtual tasks include 1) picking up objects from shelves placed against different walls of a room and placing them in a bin in the center foreground of the screen, 2) picking up eggs from a basket and cracking them over a frying pan, 3) picking up objects at a virtual supermarket and placing them in the shopping cart, 4) cleaning a stove top. In between training sessions, subjects will be encouraged to use the affected arm in daily activities. This will be assessed with the Motor Activity Log.